1. Field of the Invention
This invention relates to pneumatically operated projectile launching devices and more particularly to a bolt for such a projectile launching device including fluid flow passages configured to significantly improve the efficiency of energy transfer from a propellant gas to the projectile.
2. Description of the Related Art
Paintball is a popular recreational activity that may be played in a variety of indoor or outdoor environments. Typically, the object of the game is to capture the flag of an opposing team. Players are eliminated when xe2x80x9cmarkedxe2x80x9d by paint from a pneumatically fired paint ball. The ball is designed to rupture and splatter paint on the stricken player. The equipment used to fire the paintballs are referred to as xe2x80x9cmarkersxe2x80x9d. Paintball markers launch the paintballs by releasing a burst of gas (typically CO2 or compressed air) under pressure into a barrel behind the paintball projectile.
The development of paintball markers has been characterized by continuing efforts to improve their ease of use, reliability, accuracy and efficiency. Efficiency as used in the context of this application is intended to describe the quantity of compressed gas required to propel a paintball projectile at a predetermined velocity. The quantity of gas used is primarily a function of the input pressure, which is adjusted by a regulator between the reservoir of compressed gas and the internal mechanisms of the marker. Generally speaking, higher input pressure translates into higher paintball velocity from the marker. The rules of organized paintball games typically restrict the maximum velocity to between 280 and 300 feet per second close, e.g., within 1 to 2 feet of the muzzle of the paintball marker.
Efficiency is important to a paintball player because the power source for the paintball marker is a cartridge or bottle of compressed gas mounted to the marker. Continuing efforts have been made to reduce the size and weight while increasing the capacity of these cartridges or bottles. However, their capacity is inherently limited and a player can quite literally run out of gas. A paintball marker with improved efficiency may permit either reduction in the size and therefore weight of the compressed gas reservoir or permit the firing of more shots from a gas reservoir of the given size, or both.
Most paintball markers share some common components and are similar in some ways to a firearm or airgun. For example, the paintball projectile is fired out of a barrel, which extends from a generally closed breech end to an open muzzle end. The paintball marker typically includes a grip and utilizes a trigger to initiate launching of the paintball projectile. A reservoir or magazine of paintball projectiles is typically mounted above the breech of the paintball marker. Paintballs are typically fed into the breech of the marker by gravity, although other feeding mechanisms are available.
Many paintball markers are semi-automatic, e.g., a new projectile is loaded into firing position automatically, immediately after launch of a preceding paintball. Such paintball markers typically utilize a reciprocating bolt. The bolt serves two primary functions. First, the bolt cycles between a loading position in which the outlet of the projectile magazine is uncovered permitting a paintball to drop into the breech of the paintball marker; and a launch position in which the bolt moves toward the muzzle of the marker, covering the magazine outlet. Second, when in the xe2x80x9claunchxe2x80x9d position, the bolt re-directs a charge of compressed gas released from a chamber in the marker to propel the paintball out the muzzle end of the barrel toward a target. The expanding gas of the propellant charge transfers energy to the projectile, expelling it from the barrel of the marker. It is the efficiency of this energy transfer that ultimately determines what quantity, i.e., pressure of propellant charge is required to propel a paintball at a given velocity.
There is a need in the art for a paintball marker bolt that maximizes the efficiency of energy transfer from the released gas to a paintball projectile.
A bolt in accordance with the present invention improves the efficiency of energy transfer from the propellant charge to a paintball projectile in part by reconfiguring the gas flow passages through the bolt to reduce energy loss due to turbulence. The compactness typical of a paintball marker does not permit the propellant charge pass longitudinally from the internal reservoir through the length of the bolt and down the barrel. In a common configuration, the propellant charge enters the bolt generally perpendicular to the bolt/barrel axis through a port or opening in the side of the bolt. The flow direction of the propellant charge must be re-directed from an orientation perpendicular to the barrel to a direction aligned with the barrel.
Typical prior art bolts utilize a right-angle junction defined by the intersection of perpendicular flow passages. Such an abrupt change of direction creates turbulence in the propellant charge and robs it of energy. According to a first embodiment of a first aspect of the present invention, a marker bolt utilizes an angled inlet passage to eliminate the xe2x80x9ccornerxe2x80x9d formed at the intersection of the prior art perpendicular flow passages. This transition passage configuration simultaneously reduces the xe2x80x9cdeadxe2x80x9d volume within the bolt and reduces turbulence in the propellant charge during its change of direction. In combination, the reduced volume and turbulence of the bolt inlet transition passage reduce energy loss during the change of propellant charge direction.
Typical prior art marker bolts use a plurality of circular bores to connect the bolt inlet to the projectile end of the bolt. Such circular passages are easily machined, but make poor use of the available sectional flow area within the bolt. The resulting restricted flow path unnecessarily reduces the mass flow rate of the propulsion charge through the bolt.
According to a first embodiment of a second aspect of the present invention, a high efficiency marker bolt utilizes a plurality of equiangularly spaced, circumferentially extended longitudinal flow passages to connect the bolt inlet to the projectile end of the bolt. The passages are kidney-shaped or eliptical when viewed in section. Such passages dramatically increase the flow area through the bolt. This increased flow area presents less resistance to the propellant charge, permitting a larger quantity of propellant gas to move longitudinally through the bolt per unit of time.
The energy required to expel the paintball from the muzzle of the marker at a given velocity must be derived from the propellant charge. An object of the present invention is to provide a new and improved marker bolt that improves the efficiency of this energy transfer by minimizing the energy lost to turbulence and increasing the flow rate of the propellant charge through the bolt. These objects are achieved, in part by increasing the sectional flow area of the bolt available for longitudinal flow of the propellant charge. Less restricted gas flow permits a larger volume of the propellant charge to act on the projectile in a shorter period of time. This larger volume may in fact have a somewhat slower velocity in the longitudinal flow passages when compared to the restricted flow passages of the prior art. However, the larger volume of propellant charge reaching the projectile can accomplish more useful work, e.g., accelerating the projectile than is possible with the prior art bolt.
According to a first embodiment of a third aspect of the present invention, a high efficiency marker bolt provides a chamber connecting the longitudinal flow passages at the forward or projectile end of the bolt. This chamber serves at least two functions. First, it gives the propellant charge room to accumulate before the paintball begins to move. This room to expand smoothes the flow of the propellant charge through the marker bolt. In contrast, many prior art bolts are configured such that the paintball seats against the projectile end of the bolt, effectively covering the outlets of the circular longitudinal passages. This configuration requires displacement of the paintball before further propellant can move through the bolt. Also, covering the longitudinal passages may cause pressure waves to reflect off the paint ball back into the oncoming propellant charge. Such reflected pressure waves sap energy from the propellant charge.
Second, the chamber recombines the propellant charge portions travelling in the longitudinal flow passages into a single, more balanced volume of propellant that acts substantially uniformly on a large surface area of the paintball. Prior art bolts may impart undesirable spin to the paintball by directing unequal, high velocity streams of propellant at the is paintball. Spin on the paintball can adversely effect the accuracy of the marker.
Prior art marker bolts illustrate a chamber adjacent the projectile end of a marker bolt formed by a larger circular bore connecting the several smaller circular longitudinal passages in the bolt. The larger bore ends abruptly at an end face perpendicular to the longitudinal passages. Thus, a sharp right angle transition occurs between the longitudinal passage and the chamber. Such a configuration is easily machined but imparts turbulence to the propellant charge as it emerges from the longitudinal passages. As previously discussed, turbulence saps energy from the propellant charge that would otherwise be available for delivery to the paintball.
One embodiment of an equalizing chamber in accordance with the present invention provides an arcuate or hemispherical end face to the large circular bore defining the chamber. The intersection of the circumferentially extending longitudinal passages and the hemispherical end face of the equalizing chamber is more gradual, and therefore imparts less turbulence to the propellant charge.
An object of the present invention is to provide a new and improved bolt for a pneumatically operated projectile-launching device that reduces the quantity of compressed gas required to propel a projectile of a given configuration and mass from the barrel of a marker at a given velocity.
Another object of the present invention is to provide a new and improved bolt for a pneumatically operated projectile-launching device which improves the accuracy of the device by improving the consistency of the projectile trajectory.
A further object of the present invention is to provide a new and improved bolt for a pneumatically operated projectile-launching device that reduces turbulence in a charge of compressed gas used to launch the projectile.